Understanding environmental factors in many chronic diseases is a critical and necessary step towards the prevention of these diseases. Reaching the goal requires new tools that can accurately measure various environmental toxicants. Due to large variations in the individuals' genetic susceptibility and environmental exposure, an ideal tool must be wearable so that it can measure the toxicants in real time and within each individual's breathing zone. Several wearable devices have been developed to detect certain chemicals, or particulate matter, and they are expected to contribute to epidemiological studies. However, most epidemiological studies require a capability of assessing multiple analytes in real-time in order to accurately pin down the source of toxicants and efficiently determine if a particular analyte or a group of analytes are responsible for a disease. Pilot studies by others and us revealed that asking a subject, especially a child, to wear multiple different devices for an extended period of time faces several challenges. First, it will take substantial training resources for each child to correctly operate and for each researcher to efficiently maintain multiple devices. Second, the total weight, size and noise of multiple devices will be an unwelcome burden for a child. Third, even though each device could be inexpensive, the total cost of multiple devices can make large-scale population studies cost prohibitive. Finally, different devices have different sampling rates, internal clocks, and data collection frequencies and formats; correct interpretation and synchronization of data from these devices may be prohibitively complicated, especially when deploying them in large cohort settings. In the present project, an integrated multifunctional sensor will be developed using several innovations recently developed in the PIs' labs for real-time measurement of personal exposures. The sensor can simultaneously detect multiple important analytes, including nitric dioxide, ozone, carbon monoxide, formaldehyde, and particulate matter. These analytes are selected because they are important for studying health effects of both outdoor and indoor air pollution. In addition to the capability of detecting multiple analytes, the sensor has an embedded wireless chip that can communicate with cell phones and uses GPS and accelerometer to provide additional location and physical activity information. Finally the sensor will be miniaturized to a wearable badge size. The team will collaborate with industry to ensure quality and low cost production. The sensor development group and the epidemiologists will work together to test and validate the device.